Bash and Linux - The Terminal and the Filesystem

Before you begin, take a few minutes to check what you already know and how confident you feel. You will see the same questions again at the end of the module — this helps both you and us measure what you have learned. Click an option for every question and confidence rating, then click Next to continue.

This is your first step on the Linux side of the bridging course. You will meet the terminal, learn how the filesystem is laid out, and start moving around without a mouse. By the end you will be able to open a terminal, see where you are, list what is around you, and step in and out of folders.

• The terminal and the shell - what they are and why bash is the default.
• The Linux filesystem - a tree of folders starting from the root /.
• Your first commands - pwd, ls, cd.
• Paths - absolute vs relative, and the shortcuts ~, ., and ..

None of the commands in this lesson can damage your machine - they only read, never write. Try every one in the in-browser terminal on the right.

When you open a terminal on Linux (or macOS, or Windows with WSL) you get a window that waits for a command. The terminal is just the window. The thing reading and running your commands is the shell. bash is the default shell on almost every Linux server, including every HPC cluster you are likely to use. Everything in this course is bash.

You usually see a prompt like user@machine:~$ . The trailing $ is just a marker saying "ready". When examples show $ pwd, only type pwd.

Every shell prompt is "inside" some folder. Commands look there by default, so the first useful question is: where am I?

The answer is pwd (print working directory).

$ pwd
/home/student

On a fresh login you start in your home folder, written /home/your-username. It is the one place on the system where you can freely create, edit, and delete files without asking permission.

$ pwd

ls (list) shows the contents of the current folder. In a typical project folder for this course you might see something like a cohort dataset, a notes file, and a scripts folder:

$ ls
cohort_2026.csv  notes.txt  scripts  vitals

ls on its own does not tell you which entries are files and which are folders. Flags fix that. Flags are short options written with a leading dash.

• ls -l - long format: one entry per line, with size, owner, and date.
• ls -a - show hidden entries (filenames starting with a dot).
• ls -lh - long format with sizes in human units (K, M, G).
• ls -lt - long format sorted by modification time, newest first.

$ ls -lh
total 16K
-rw-r--r-- 1 student staff 5.1K May 24 10:25 cohort_2026.csv
-rw-r--r-- 1 student staff  105 May 23 18:01 notes.txt
drwxr-xr-x 2 student staff 4.0K May 24 10:22 scripts
drwxr-xr-x 2 student staff 4.0K May 24 10:22 vitals

Flags combine: ls -lh and ls -hl mean the same thing. You can also list another folder by passing its name: ls vitals shows what is inside vitals without stepping into it.

$ ls
$ ls -l
$ ls -lh
$ ls -lh vitals

$ ls
$ ls -a
$ ls -la

cd (change directory) steps into a folder:

$ pwd
/home/student
$ cd vitals
$ pwd
/home/student/vitals

cd .. goes up one level. cd on its own (or cd ~) jumps back to your home folder from anywhere.

$ cd ..
$ pwd
/home/student
$ cd vitals
$ cd
$ pwd
/home/student

If you cd into something that does not exist, bash tells you so and leaves you where you were:

$ cd vitls
bash: cd: vitls: No such file or directory

$ cd vitals
$ pwd
$ cd ..
$ pwd
$ cd ~
$ pwd

A path is an address that tells the shell how to find a file or folder. There are two kinds.

An absolute path starts with / and describes the location from the root of the filesystem. It means the same thing no matter where you currently stand.

/home/student/cohort_2026.csv
/usr/bin/python3
/var/log/syslog

A relative path does NOT start with /. It is read relative to your current folder. If you are in /home/student and type cd vitals, the shell looks for vitals inside /home/student. From anywhere else the same command would look somewhere else.

• ~ - your home folder, anywhere on the system.
• . - the current folder.
• .. - the parent folder, one level up.
• / - the root of the entire filesystem.

$ cd ~
$ pwd
/home/student
$ cd /
$ pwd
/
$ ls
bin  boot  etc  home  tmp  usr  var

You will mix and match. cd ~/vitals jumps to vitals inside your home. cd ../scripts pops up one level then into a sibling folder.

$ cd /
$ pwd
$ ls
$ cd ~
$ pwd
$ cd vitals
$ cd ..
$ cd ~/scripts
$ pwd

$ cd ~/scripts
$ pwd
$ cd ../vitals
$ pwd
$ cd /home/student/vitals
$ pwd

Linux is case sensitive. Patients and patients are two different folders. If "No such file or directory" surprises you and the file is there, check the capitals.

Spaces in filenames are awkward. cd My Notes does not work - bash sees two arguments. Quote it (cd "My Notes") or escape the space (cd My\ Notes).

You have reached the end of the module. Try the same questions again — your answers here, paired with your pre-test answers, are how we measure what the module taught you. Answer every question and confidence rating, then click Submit and see results to view your score.

Here is how your post-test answers compare with your pre-test answers. The pre/post pairing is the most reliable way to see what this module actually taught you.